Subject : Offshore Drilling

If the sea condition at the proposed drilling points is relatively calm, we will perform the offshore drilling using pontoon instead of platform.

For your information offshore drilling is influenced by sea condition. At the area with relatively calm sea condition to slightly rough sea condition, the drilling still can be done using a pontoon. In such area the drilling can be done using a pontoon even at sea water depth of 15m. The advantage of using a pontoon is the easy to move it from one offshore drilling point to the other drilling point and thus only one pontoon is needed for every offshore drilling point, Besides construction of the pontoon can be done on land. It is easier than constructing a platform over offshore drilling point.

The size of pontoon will be about 5x5m2. During the drilling the pontoon will be strongly anchored at its corners. Double casing if necessary will be installed, especially in the upper part, between sea floor and the pontoon. The disadvantage of drilling on pontoon is that on rough sea condition the drilling will be difficult.

Drilling procedures will meet in-situ conditions, for examples: drilling in soil clay or sandy materials, will be drilled by dry drilling method or “Continuous Coring” method instead of “Wash Boring”. The continuous coring is the most reliable drilling method soil investigation work. In this method the drilling is done without water flushing, the core samples is obtained by single core barrel on dry drilling process and there is no softening on soil formation due to water flushing, in the other hand wash boring is a drilling method using water flushing to penetrate the soil layer, no core sample is obtained except sludge sample and there will be softening process on soil formation causing unreliable result of field test (SPT) and also laboratory test. The description of core will be done by soil engineer or geologist, based on USCS (United Soils Classification System) standard and description suggested by ISRM (International Society for Rock Mechanic).

The list below is our previous experiences in offshore drilling on similar condition which we did successfully using a pontoon as the following : Offshore drilling for Maspion Jetty in Gresik at 3.5 km from shore line at Madura strait at

location with sea water depth of -15m Offshore drilling for jetty of PT.IKPP Merak with Luis Berger Consulting Engineers at the

locations with water depth -18m Offshore drilling for Batu Licin cement jetty at South Kalimantan for Kawasaki Steel at the

location with water depth -12m Offshore drilling for Power Plant project at Paiton and Batam for Dongfang-China at

location with water depth of 12 – 17m And many others offshore drilling projects (more than 30 projects) which we did

successfully using a pontoon.

Note :Based on the map, the offshore drilling location at the proposed jetty area is on relatively open sea. The sea condition in such area can be predicted will be rough / not calm enough. It means offshore drilling will be difficult to be done on floating pontoon and it must be done on fixed platform.